Effects Of Frozen Storage Of Raw Pork On The Formation Of Advanced Glycation End-products In Meat Products

Advanced glycation end-products(AGEs),reaction products of amino groups with carbonyl compounds,are substances with stable chemical structure and harmful to human health.AGEs are formed mainly by the body’s metabolism and dietary intake.In order to reduce the harm of AGEs to human body,it is meaningful to research the formation mechanism of AGEs in foods.As a good source of nutrients,such as protein and fat,meat was often selected to study AGEs in meat and meat products.Frozen storage is common in the meat industry due to its economy and convenience.Usually,raw pork used in meat products is often frozen at-18 ~oC for long periods of time,which inevitably leads to protein or lipid oxidation.However,different levels of oxidized protein or lipid showed vary effects on AGEs formation in meat products.Therefore,the objective of this study was to investigate the effects of frozen storage time of raw pork on the physical and chemical indexes of myofibrillar proteins(MPs),properties of myofibrillar protein gels and the generation of AGEs in meatballs.The results could be used to research the formation mechanism of AGEs in meat products,thereby providing a theoretical reference for reducing the intake of dietary AGEs.The main contents and results of this study are as follows:(1)Effect of frozen storage time on the oxidation degree of porcine MPs.Raw pork was stored at-18℃for different time(0,1,4,8,12 weeks),and used for the extraction of MPs.Then protein oxidation parameters(carbonyl,total sulfhydryl group,free amino groups,surface hydrophobicity and endogenous tryptophan fluorescence)were determined.The results suggested that,carbonyl content increased significantly(P<0.05),and total sulfhydryl group,free amino groups,surface hydrophobicity and endogenous tryptophan fluorescence content generally showed a decreasing trend(P<0.05).There is a correlation between storage time and carbonyls,total sulfhydryl group,free amino groups or surface hydrophobicity.Therefore,MPs will be oxidized during the frozen storage,resulting in the degradation of raw meat quality.(2)Effect of frozen storage time on properties of myofibrillar protein gels.Raw pork was stored at-18℃for different time(0,1,4,8,12 weeks),and used for the extraction of MPs and preparation myofibrillary protein gels.The properties of myofibrillar protein gels were investigated by measuring thiobarbituric acid-reactive substances(TBARS),solubility of MPs,water-holding capacity of myofibrillar protein gels,whiteness of myofibrillar protein gels and strengths of myofibrillar protein gels.The results suggested that,TBARS value increased,and solubility of MPs,water-holding capacity of myofibrillar protein gels,whiteness of myofibrillar protein gels and strengths of myofibrillar protein gels showed a decreasing trend.Therefore,MPs were oxidized during the frozen storage,which significantly affected properties of myofibrillar protein gels.(3)Impact of frozen storage duration of raw pork on the formation of advanced glycation end-products in meatballs.Meatballs were prepared using frozen raw pork(-18 ~oC,0,30,60,90 and 120 days),and N~ε-(carboxymethyl)lysine(CML)and N~ε-(carboxyethyl)lysine(CEL)(typical AGEs)were determined.The results suggested that,CML contents in meatballs increased from 13.26(0 day)to 43.30 mg/kg protein(120 days),and CEL levels increased from 12.37(0 day)to 40.50 mg/kg protein(120days)with the increasing frozen storage time of raw pork.Furthermore,oxidative damages of raw pork(carbonyls,total sulfhydryl groups,free amines,the surface hydrophobicity,TBARS of residual lipids and intrinsic tryptophan fluorescence intensity)were assessed during frozen storage.A significant correlation between MPs oxidation and CML/CEL contents was observed,which indicated that oxidative damages to raw pork during frozen storage could promote the generation of CML and CEL in meatballs.Therefore,control of MPs oxidation in raw pork may facilitate the reduction of AGEs generation in meatballs.